diff options
Diffstat (limited to 'cpus.c')
| -rw-r--r-- | cpus.c | 37 |
1 files changed, 31 insertions, 6 deletions
@@ -132,7 +132,7 @@ typedef struct TimersState { static TimersState timers_state; /* Return the virtual CPU time, based on the instruction counter. */ -int64_t cpu_get_icount(void) +static int64_t cpu_get_icount_locked(void) { int64_t icount; CPUState *cpu = current_cpu; @@ -148,6 +148,19 @@ int64_t cpu_get_icount(void) return qemu_icount_bias + (icount << icount_time_shift); } +int64_t cpu_get_icount(void) +{ + int64_t icount; + unsigned start; + + do { + start = seqlock_read_begin(&timers_state.vm_clock_seqlock); + icount = cpu_get_icount_locked(); + } while (seqlock_read_retry(&timers_state.vm_clock_seqlock, start)); + + return icount; +} + /* return the host CPU cycle counter and handle stop/restart */ /* Caller must hold the BQL */ int64_t cpu_get_ticks(void) @@ -249,8 +262,9 @@ static void icount_adjust(void) return; } - cur_time = cpu_get_clock(); - cur_icount = cpu_get_icount(); + seqlock_write_lock(&timers_state.vm_clock_seqlock); + cur_time = cpu_get_clock_locked(); + cur_icount = cpu_get_icount_locked(); delta = cur_icount - cur_time; /* FIXME: This is a very crude algorithm, somewhat prone to oscillation. */ @@ -268,6 +282,7 @@ static void icount_adjust(void) } last_delta = delta; qemu_icount_bias = cur_icount - (qemu_icount << icount_time_shift); + seqlock_write_unlock(&timers_state.vm_clock_seqlock); } static void icount_adjust_rt(void *opaque) @@ -292,10 +307,14 @@ static int64_t qemu_icount_round(int64_t count) static void icount_warp_rt(void *opaque) { - if (vm_clock_warp_start == -1) { + /* The icount_warp_timer is rescheduled soon after vm_clock_warp_start + * changes from -1 to another value, so the race here is okay. + */ + if (atomic_read(&vm_clock_warp_start) == -1) { return; } + seqlock_write_lock(&timers_state.vm_clock_seqlock); if (runstate_is_running()) { int64_t clock = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); int64_t warp_delta; @@ -306,14 +325,15 @@ static void icount_warp_rt(void *opaque) * In adaptive mode, do not let QEMU_CLOCK_VIRTUAL run too * far ahead of real time. */ - int64_t cur_time = cpu_get_clock(); - int64_t cur_icount = cpu_get_icount(); + int64_t cur_time = cpu_get_clock_locked(); + int64_t cur_icount = cpu_get_icount_locked(); int64_t delta = cur_time - cur_icount; warp_delta = MIN(warp_delta, delta); } qemu_icount_bias += warp_delta; } vm_clock_warp_start = -1; + seqlock_write_unlock(&timers_state.vm_clock_seqlock); if (qemu_clock_expired(QEMU_CLOCK_VIRTUAL)) { qemu_clock_notify(QEMU_CLOCK_VIRTUAL); @@ -327,7 +347,10 @@ void qtest_clock_warp(int64_t dest) while (clock < dest) { int64_t deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL); int64_t warp = MIN(dest - clock, deadline); + seqlock_write_lock(&timers_state.vm_clock_seqlock); qemu_icount_bias += warp; + seqlock_write_unlock(&timers_state.vm_clock_seqlock); + qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL); clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); } @@ -391,9 +414,11 @@ void qemu_clock_warp(QEMUClockType type) * you will not be sending network packets continuously instead of * every 100ms. */ + seqlock_write_lock(&timers_state.vm_clock_seqlock); if (vm_clock_warp_start == -1 || vm_clock_warp_start > clock) { vm_clock_warp_start = clock; } + seqlock_write_unlock(&timers_state.vm_clock_seqlock); timer_mod_anticipate(icount_warp_timer, clock + deadline); } else if (deadline == 0) { qemu_clock_notify(QEMU_CLOCK_VIRTUAL); |